In complex manufacturing processes, it is frequently necessary to monitor the chemical, mechanical, metallurgical or other characteristics during the process. In particular, chemical composition manufacturing processes monitored by x-ray spectroscopy require the sampled material to be positioned to reflect or refract a beam of x-ray to a measuring detector, wherein position deviations by a few parts of a mil cause significant variations in analysis readings.
In a typical sample changer, samples, comprising rectangular samples of compressed material approximately 3.times.4 cm., are arranged in a linearly spaced tray of approximately 35 cm. in length and are retained within the sample tray by forces provided by spring elements. The sample tray is received by and moveable in a generally u-shaped channel piece of approximately twice the length of the sample tray, at about the center of which is a mechanism for which mechanically forces a selected sample through the bottom of the tray into a position defined on one surface by fixed, rigid members, and retained by spring members. The positioning and sample retaining spring members become fatigued and deformed over time and use, causing the apparatus to jam or otherwise improperly function. Furthermore, the spring retention typically used is relatively intolerant of accumulated residual particulate matter from the samples, causing wearing or displacement of the samples from the desired position. Moreover, so critical is the position of the sample x-ray spectroscopy that s significant sample displacement is dependent on the position of the sample tray within its channel. In particular, when the bulk of the sample tray is at either extreme, that is forward or rearward, sufficient bending of the support mechanism causes a variation in the x-ray spectroscopy reading of the sample.
Moreover, prior art sample changers have required the operator to place the samples in a particular sequence and in order, making it virtually difficult or inconvenient to operate or to attempt to adjust the weight of the sample tray by positioning the samples therein. Thus, the existing changers provide marginal reliability and problematic operation.